There's a Coke/Pepsi evaluation out somewhere on a car-truck-hotrod internet site of the most popular (read expensive) sound deadeners and the cheapest, Peal and Seal. P + S is just as good as if not better than the products several times its cost. Doubling up? I don't know if one can expect double or a significant difference from one as opposed to two layers. I think Harbor Freight sells a cheap decibel meter where you could do your own scientific work.
I have one layer of p+s but not the roof, will do the roof one of these days. The neatest application is one 6" strip the width of each door that takes it from oil-canning sound to a much quieter (in my opinion) closure.
In addition, P+S is used in conjunction with other products to achieve various end goals of sound/heat reduction, it's not a one product does all.
~ Cosmo
1949 Chevy Half Ton
Rocinante, like Don Quixote, he is awkward, past his prime, and engaged in a task beyond his capacities.
"...my good horse Rocinante, mine eternal and inseparable companion in all my journeys and courses." ...Don Quixote, Cervantes
"If you come to a fork in the road, take it."...Yogi Berra
"Rudeness is the weak man's imitation of strength." ...Eric Hoffer
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